Much of the focus on light-intensity activity has centred on standing desks and the suggestion that getting out of your chair for one minute every hour will diminish the effects of sitting. But the amount of science backing that up is surprisingly thin.LIONEL BONAVENTURE / AFP/Getty Images files

Defining exercise used to be easy. Any activity that causes your heart to beat faster, your breath to accelerate and a bead or two of sweat to develop was exercise. Everything else wasn’t.

That’s beginning to change, as health experts start exploring a whole new body of research devoted to the spectrum of physical activity that lies between working up a sweat and sitting on the couch.

This low level of activity used to be classified as sedentary, which in large doses is detrimental to health. The key to combating the ill effects of being sedentary, said the experts, is exercise — in particular 150 minutes of moderate or 75 minutes of vigorous activity a week, or about 30 minutes of physical activity a day.

But the discovery that it takes more than a daily dose of exercise to combat the consequences of too much time spent sitting caused a rethink in how we oppose sedentary behaviour. Also fine-tuned was the definition of sedentary, which is said to be any waking behaviour with an energy expenditure less than or equal to 1.5 METs (metabolic equivalent of task) while in a sitting, reclining or lying posture. (One MET equals the energy expended by an individual while seated at rest.)

So how do we refer to the continuum of movement between sitting on the couch and working up a sweat?

Welcome yet another definition in the expanding dictionary devoted to physical activity. Light-intensity activities include any movement that expends 1.5 to three METs of energy, including standing.

Does that mean we should refer to the increasingly large number of people who spend most of their waking hours somewhere between sitting and exercising as being sedentary or active?

We’re not sure.

Confused? I don’t blame you. Maybe this example will help illustrate the problem: you take a 30-minute brisk walk every morning, but spend the rest of the day sitting — in the car during your commute, at your desk over the course of the workday and on the couch at night. Technically, you meet the recommended weekly exercise quotient, but most of your waking hours are still spent sitting. Are you active or sedentary?

Compare that lifestyle to a dentist, teacher or construction worker who never exercises but spends most of the workday on their feet and moving. Are they sedentary or active?

The answers to these questions are being debated. What isn’t up for debate is the impact technology has had on day-to-day life. Most people, even those traditionally viewed as active, now spend a good part of their day sitting in front of a screen. And while some exercise is always better than no exercise, the latest estimate is that it takes four to five times the recommended 150 minutes of moderate-intensity exercise a week to diminish the increased risk of metabolic disease and mortality associated with too much time spent sitting.

So what does it take to minimize the health risks of all that sedentary time? It’s ambitious to think we can get those already struggling with being active for 150 minutes a week to sweat more often. But it is possible that we can get them to move more often, which is where light-intensity activity comes in.

Most of the focus on light-intensity activity has centred on standing — especially the use of standing desks and the suggestion that getting out of your chair for one minute every hour will diminish the effects of sitting. But the amount of science substantiating these claims is surprisingly thin. In fact, the science exploring how to best combat the ill effects of a sedentary lifestyle is still in its infancy.

What we do know is that sitting only becomes a health risk when it exceeds seven hours a day, which means it’s OK to relax in your favourite chair within reason. What we don’t know is what types of light physical activity best diminish the health risks associated with long hours spent in a chair. We also need to know how often and how long we need to move. Is one minute of standing really enough to diminish the physiological impact of 59 minutes spent sitting? Or should we walk on the spot, down the hall or up a flight of stairs every time our activity monitor reminds us to get out of the chair?

Until that data starts rolling in, we need to think about exercise in more ways than just focusing on either end of the activity spectrum. After all, even if everyone increased their daily exercise goal to 45 minutes, that still leaves a lot of minutes in the day to be sedentary. And getting rid of sitting altogether is unlikely, and unnecessary. Instead, we need to find a better balance between the amount of sedentary, light, moderate and vigorous activity in our day. And we need to expand our definition of exercise to include a larger spectrum of movement, with the understanding that any and all physical activity is good for health.

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